全文获取类型
收费全文 | 1745篇 |
免费 | 78篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 75篇 |
综合类 | 3篇 |
化学工业 | 364篇 |
金属工艺 | 44篇 |
机械仪表 | 54篇 |
建筑科学 | 19篇 |
能源动力 | 40篇 |
轻工业 | 146篇 |
水利工程 | 2篇 |
无线电 | 268篇 |
一般工业技术 | 355篇 |
冶金工业 | 322篇 |
原子能技术 | 40篇 |
自动化技术 | 95篇 |
出版年
2023年 | 10篇 |
2022年 | 15篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 34篇 |
2017年 | 26篇 |
2016年 | 40篇 |
2015年 | 29篇 |
2014年 | 49篇 |
2013年 | 88篇 |
2012年 | 58篇 |
2011年 | 74篇 |
2010年 | 52篇 |
2009年 | 66篇 |
2008年 | 82篇 |
2007年 | 50篇 |
2006年 | 50篇 |
2005年 | 72篇 |
2004年 | 36篇 |
2003年 | 41篇 |
2002年 | 55篇 |
2001年 | 37篇 |
2000年 | 32篇 |
1999年 | 41篇 |
1998年 | 134篇 |
1997年 | 89篇 |
1996年 | 55篇 |
1995年 | 42篇 |
1994年 | 48篇 |
1993年 | 37篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 28篇 |
1989年 | 16篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 21篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 17篇 |
1976年 | 14篇 |
1973年 | 6篇 |
1970年 | 3篇 |
排序方式: 共有1827条查询结果,搜索用时 109 毫秒
961.
Pierre Eyben Danielle Vanhaeren Thomas Hantschel Kanna Adachi 《Microelectronic Engineering》2007,84(3):437-440
Within this work, we have studied ultrathin n- and p-type extension implants in order to evaluate the junction delineation accuracy and reproducibility of the SSRM technique on ultra-shallow implants. This is a challenging task since it needs a technique that has simultaneously good sensitivity (<10%), high spatial resolution (1-3 nm) and high dopant gradient resolution (1-2 nm/dec). For every device, two different samples were prepared and measured separately. Unparallel reproducibility capabilities of the technique have been demonstrated as well as a sub-nanometer reproducibility for the lateral diffusion analysis. Regarding junction depths, reproducibility is 1-3 nm where the main uncertainty is the varying silicide thickness. 相似文献
962.
963.
Joint of silicon nitride and molybdenum with vanadium foil,and its high-temperature strength 总被引:2,自引:0,他引:2
Joints of silicon nitride and molybdenum with a vanadium interlayer were fabricated using a vacuum hot-pressing facility. The optimum joining conditions for producing a joint with the highest shear strength were found to be as follows: a temperature of 1328 K, a mechanical pressure of 20 MPa and a bonding time of 5.4 ks. The effect of test temperature on shear strength was also examined. The strength level was initially 118 MPa at room temperature and this level gradually decreased as the test temperature rose. At 973 K, the strength level was still 70 MPa. Observations of the interface by scanning electron microscopy (SEM) and electron probe X-ray microanalysis (EPMA) revealed that a layer of reaction product V3Si formed at the silicon-nitride-vanadium interface. 相似文献
964.
This study was conducted to explore whether anthropometric indices of obesity are associated with atherogenic risk factors in young adult working women in Japan. The subjects were 492 women in an occupational setting. Predictor variables were body mass index (BMI), the sum of triceps and subscapular skinfold thickness (SFT), and the waist to hip ratio (WHR). Outcome variables were serum total cholesterol, triglyceride and blood pressures. The average age of the subjects was 26.3 (SD 3.9) years. The upper quartiles of BMI and SFT were significantly associated with all atherogenic risk factors, while the upper quartiles of WHR were not. Multiple comparisons revealed the 4th quartiles of BMI (> 22.25) and SFT (> 39 mm) to have significantly higher values for all atherogenic risk factors. We found that BMI and skinfold thickness were more relevant to the prediction of atherogenic risk factors than WHR in young adult Japanese women. 相似文献
965.
966.
A novel ventilation type dehumidifier with heat-flow controllable heat exchanger was installed on the wall of a greenhouse. Dehumidification and heat recovery experiments were conducted. The construction of the novel dehumidifier is simpler than that of the conventional dehumidifier with a compressor. It was found that the required input for the ventilation type dehumidifier was less than that of a conventional dehumidifier with compressor. 相似文献
967.
Applications of conjugated polymers (CP) in organic electronic devices such as light-emitting diodes and solar cells depend critically on the nature of electronic energy transport in these materials. Single-molecule spectroscopy has revealed their fundamental properties with molecular detail, and recent reports suggest that energy transport in single CP chains can extend over extraordinarily long distances of up to 75 nm. An important question arises as to whether these characteristics are sustained when CP chains agglomerate into a neat solid. Here, we demonstrate that the electronic energy transport in aggregates composed of tens of polymer chains takes place on a similar distance scale as that in single chains. A recently developed molecular-level understanding of solvent vapour annealing has allowed us to develop a technique to control the CP agglomeration process. Aggregates with volumes of at least 45,000 nm(3) (molecular weight ≈ 21 MDa) maintain a highly ordered morphology and show pronounced fluorescence blinking behaviour, indicative of substantially long-range energy transport. Our findings provide a new lens through which the ordering of single CP chains and the evolution of their morphological and optoelectronic properties can be observed, which will ultimately enable the rational design of improved CP-based devices. 相似文献
968.
H. Sasakura Y. Akagi M. Tanaka S. Tsukui M. Adachi 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1623-1626
New Pb-based 1222 cuprates containing phosphorus have been synthesized in the (Pb,P)Sr2(Eu,Ce,Sr)2 Cu2O
z
system. From X-ray powder diffraction study, almost the single 1222 phase samples are found to be obtained in a considerable
wide composition area of 0.3≤x≤1.2 for the nominal composition of (Pb0.75P0.25)Sr2(Eu1.9−x
Ce
x
Sr0.1) Cu2O
z
. The crystal structure for each sample has a tetragonal symmetry and the typical lattice parameters are a=0.3851 nm and c=2.922 nm. After annealing under 143 atm O2 atmosphere at 400 °C, a sample with x=0.3 among the almost-single phase samples shows an onset of resistivity-drop at the highest temperature of about 22 K and
zero-resistivity at the highest temperature of about 12 K, then this sample also shows an onset of diamagnetic signal at about
20 K. These phenomena are found to originate from superconductivity of the new 1222 phase. 相似文献
969.
Masashi Tanaka Hiroyuki Sasakura Yoshiya Akagi Shigeki Tsukui Motoaki Adachi 《Journal of Superconductivity and Novel Magnetism》2011,24(5):1673-1676
We already reported on the synthesis of new Pb-based 1212 layered cuprates containing sulfur in the (Pb0.75S0.25)Sr2(Y,Ca)Cu2O
z
system. There none of the samples showed superconductivity until after annealing under high O2 pressure. More recently, we have discovered that the samples could be substituted by Ba for Sr up to x=0.6 in the composition of (Pb0.75S0.25)(Sr2−x
Ba
x
)(Y0.4Ca0.6) Cu2O
z
. Then if the Ba-substitution is performed for Sr, some of the almost-single phase samples are found to show resistivity drops
and magnetic anomalies without annealing under high O2 pressure. Among the samples, a sample with the nominal composition of (Pb0.75S0.25)(Sr1.5Ba0.5)(Y0.4Ca0.6) Cu2O
z
is found to show the highest onset temperatures of a resistivity drop at about 35 K and a magnetic anomaly at about 31.5
K. These are higher than the highest values for the superconducting Ba-free sample of (Pb0.75S0.25)Sr2 (Y0.4Ca0.6)Cu2O
z
which was annealed under high O2 pressure. 相似文献
970.
Phase-shifting digital holography is applied to the measurement of the surface profile of the inner surface of a pipe for the detection of a hole in its wall. For surface contouring of the inner wall, a two-wavelength method involving an injection-current-induced wavelength change of a laser diode is used. To illuminate and obtain information on the inner surface, a cone-shaped mirror is set inside the pipe and moved along in a longitudinal direction. The distribution of a calculated optical path length in an experimental alignment is used to compensate for the distortion due to the misalignment of the mirror in the pipe. Using the proposed method, two pieces of metal sheet pasted on the inner wall of the pipe and a hole in the wall are detected. This shows that the three-dimensional profile of a metal plate on the inner wall of a pipe can be measured using simple image processing. 相似文献